High-phosphorus scale-resisting steel



Patented Apr. 2, 1929.

UNITED, STATES 1,707,364 PATENT OFFICE.

FRANK R. PALMER, OE READING, PENNSYLVANIA, ASSIGNOR TO THE CARPENTER STEEL COMPANY, OF READING, PENNSYLVANIA, A CORPORATION OF NEW JERSEY.

HIGH-PHOSPHORUS SCALE-RESISTING STEEL.

No Drawing. Application filed July 10,

, This inyention relates to i an improved scale-reslstlng steel or ferrous alloy intended particularly for the production of shaped articles of: manufacture which are required to maintain a stable non-corrosive surface though subjected to high temperatures such as occur in automobile engines and other uses. Andit consists essentially in the deliberate provision in the alloy of a content of phos phorus adapted to efiectively and economically impart the desired quality thereto without deleterious effect for the intended purposes.

Phosphorus has unintentionally appeared heretofore generally as a recognizedly injurious element; the elimination of it to a maximum content of 05%, being commonly deemed a commercial requirement in alloy steels, as is specifically prescribed for instance in the standard specifications of the Society of Automotive Engineers and the American Society for Testing Materials;

though in the simple carbon steels il, l)l 1OS- phorus content as highas .125 has been accepted for the securing of greater machineability, notwithstan'dingthe generally objectionable brittle quality imparted thereby.

My invention is based upon the discovery and practical development of the fact that phosphorus, heretoforecommonly treated as an incidental impurity requiring elimination, may be deliberately employed to determined advantage in percentages which are high relative to those ordinarily tolerated in actual manufacture.

The practical development of this discovery, based on extensive experimentation and investigation, has shown that this heretofore commonly. worse than worthlesselement, may be utilized in relatively high percentages,'even in simple-steels, to satisfactorily impart a considerable degree of scale-resistance quality; and that in connection with comparatively small quantities of other elements, as chromium and silicon, heretofore known to impartsuch quality in alloy steels, it greatly adds to such desired 7 effect, serving not only as an economical and efficient substitute for increased quantity of: the relatively expensive element or elements, but carrying such desired effect farther than is attainable by such elements alone.

In more specifically setting forth the in- I vention as developed by considerable experimentation, preliminary statement will be 1926. Serial No. 121,738.

made in definite percentages, of the content of a ferrous alloy which embodies the invention satisfactorily, and completely as now appears; as follows: carbon .40%; phosphorus .150; chromium 300%; silicon 2.00%; molybdenum 50%.

It is to be understood that the particular formula above specifically noted may be readily varied within the scope of my invention as further described hereinafter and defined in the subjoined claims; that any content of incidental elements, suclr as manganese and sulphur, is ignored; that the chromium, silicon, and molybdenum contents noted provide a very satisfactory basis for effective use of the high phosphorus content indicated by the preferred percentage noted; that the chromium and silicon contents indicate the preferable restricted use of these known elements when used jointly in connection with my high phosphorus content the chromium content being increased when the siliconis omitted; that the molybdenum element is included as advantageously serving in the present alloy, its known purposes, namely the increasing of the so-called rcdhardness and toughness. As to the essential novel element, high phosphorus, the stated content is approximating that which has been found to be most efficacious in proportion to the quantity used. It is noted however, that my actual use indicates that any increase in this percentage of phosphorus increases correspondingly though less rapidly the dcsired scale-resisting quality up to a maximum of approximately .50%-about where also an objectionable brittleness effect is develpped; and that decrease of this stated content (15%) reduces correspondingly though more rapidly the scale-resisting effect produced,sueh effect practically disappearing in alloy steels when a less percentage of phosphorus is used than 05%, and being practically unimportant withless than 08%; also that when the high phosphorus content is provided in an otherwise ordinary simple carbon steel, without content of the heretofore known scale-resisting elements as chromium and silicon mentioned,that the percentage of phosphorus provided should be in excess of to provide satisfactory effect and up to .50% as stated.

As indicating the actual scale-resisting effect of deliberately employed phosphorus in relatively high percentages heretofore pracmium was required to be added to No. 1 in tically prohibited, as contemplated by my invention, I mention as examples the following alloy steels among many machined and ground specimens practically tested z t-he preferred content of carbon, chromium, and sili con stated above being employed in both, with a low phosphorus content in one and a high phosphorus content in the other:

- Chro- Phos- Carbon Silicon mium phorus Per Per Per Per cent ce'nt cent cent No.1 0.40 2.00 3.00 0.047 No.2 .40 2.00 g 3.00 .157

These specimens being heated to 1600 1 in air, for eight hours, No. 1 acquires a loose peeling scale, while No. 2 shows only a bronze tarnish color with no scale at all. Further tests show that five per cent additional ehroorder to make it approach the scale resistance of No. 2; showing great economy in the employment of the high phosphorus content in the latter with equal desired effect.

Having in'mind the practical difliculties of accurately determining actual effects of various percentages of the phosphorus, in connection with the use of other elements in various proportions,.it will be understood that the main effects are clearly set forth above with full disclosure for practical use;

that While the invention provides for the use of phosphorus only in actually small percentages of the mass, such percentages are so high relative to the percentages heretofore tolerated or permissible in commercial use, as to warrant distinguishing this improved alloy as a highphosphorus steel or ferrous alloy, notwithstanding that such designation runs counter to a strong existing prejudice against such content in commercially desirable steels.

My improved alloy steel can be readily and satisfactorily produced by the usual crucible pot melting method, by compounding with an iron base the ferro alloys ordinarily used for adding the stated elements.

What I claim is:

1. A scale-resisting alloy steel containing carbon less than 1.50%, phosphorus .05 to chromium 3% to 30%.

2. A scale-resisting alloy steel containing carbon less than 1.50%, phosphorus .05 to 50%, chromium 3% to 30%, molybdenum .10 to 2.00%.

3. A scale-resisting alloy steel containing carbon 05% to 1.50%, phosphorus 05% to 50%, chromium 1.00% to 30.00%, silicon 1.00% to 5.00%.

4. A scale-resisting alloy steel containing carbon 05% to 1.50%, phosphorus 05".) to 50%, chromium 1.00% to 30.00%, silicon 1.00% to 5.00% and molybdenum .10% to 2.00%.

5. A scale-resisting alloy steel containing the following elements in approximately the stated proportions, namely, carbon 40%, chromium 3.00%, silicon 2.00%, phosphorus .15%.

6. A scale-resisting alloy steel containing the following elements in approximately the stated proportions, namely, carbon 40%, chromium 3.00%, silicon 2.00%, phosphorus 15%, molybdenum 50%.

In testimony whereof I affix my signature.

FRANK R. PALMER. 

